This invention relates generally to chemical treatment of producing oil wells and more specifically to a system for automatically treating such wells without human intervention.
Producing oil wells contain a variety of corrosives. These corrosives are mixed with the well fluids, such as petroleum and water, and cause damage to the various parts of the well, especially the down hole pump and production tubing. These corrosives can be counteracted by introducing liquid treatment chemicals into the well. Use of such chemicals prevents corrosion of the various parts of the well, and greatly extends its life. The treatment chemical is easily separated from the desired petroleum along with water and other well fluids.
Several methods are presently in use to chemically treat producing oil wells. One very common method is to introduce a continuous stream of treatment chemical into the well during production. This is usually accomplished through the use of a small treatment chemical pump connected to the mechanism of the larger well pump. This pump is located above ground, and constantly introduces a small amount of chemical into the well on a continuous basis while the well pump is in operation. This treatment chemical falls to the bottom of the well, where it mixes with the other well fluids. The chemical counteracts corrosives at the bottom of the well, and in the production tubing as it is pumped to the surface along with the remaining well fluids. The chemical is easily separated from the petroleum after production, although it is not reusable.
Another common method of well treatment involves introducing a measured portion of treatment chemical into the well, and recirculating the well fluids containing such chemical throughout the well for a period of time. A typical means of accomplishing this type of treatment is to have a truck containing the treatment chemical drive to each well site. When the truck reaches the well site, the well is shut down, and a hose is coupled from the truck to piping leading into the well casing. Two or more valves are operated, so that well fluids brought to the surface through the production tubing are recirculated back into the well casing. A predetermined amount of chemical is then pumped into the well casing, and the well pump restarted. The well fluids mix thoroughly with the treatment chemical, and this mixture is circulated throughout the well for a predetermined period of time. The well is then stopped, and the valves are reset in their original state. The well pump is then restarted, and resumes production. The treatment operator then moves on to the next site.
A variation of this recirculation method involves storage of chemical on site instead of being brought in by truck for each treatment. An operator shuts down the well, and introduces chemical from the on site holding tank instead of from the truck. Otherwise, this method is the same as just outlined.
Present methods of chemically treating producing oil wells have a number of drawbacks. The continuous method of treating a well is wasteful of the treatment chemical. The chemical which is introduced into the well makes only a single pass through the well piping, and is then discarded with the production fluids. This single pass through the well does not allow the treatment chemical to be fully utilized. Therefore, excess chemical must be introduced so that the well will be properly treated at this low efficiency.
The recirculation method has advantages in that it can more fully utilize the non-corrosive properties of the treatment chemical, but has a number of important drawbacks of its own. The requirement of a human operator, whether he transports treatment chemical with him or merely utilizes that stored on site, means that treatment of the well is very often on an erratic basis and off schedule. When a well is treated with the recirculation method, it is important that it is treated for a predetermined period of time at a predetermined frequency. Poor weather conditions, as well as sickness and so forth, often prevent a human operator from treating the well at the proper time, and several treatment periods may be missed entirely. This can cause damage to the well, and repeated instances of missing treatment periods or mistiming them may eventually necessitate a shut-down for repairs.
Additionally, the conditions at each well usually differ somewhat from those of other wells, calling for treatment times of various lengths and various frequencies. In addition to the possibility of mistake on the part of the human operator, whereby treatment times and frequencies for various wells are accidentally interchanged, the varying period between treatments for each well means that eventually the human operator must treat some wells at a time which approximates the planned treatment time. On a fairly frequent basis, the treatment schedule requires that the operator treat wells at one time, which of course he cannot do. Therefore, a certain amount of juggling in treatment schedules is required. This situation is worsened when bad weather or other nonproduction related influences interfere.
A certain amount of production time is lost when the operator sets up the recirculation state for the well. The well pump must be shutdown and restarted twice, and the valves must be operated. This time loss is not extreme, but can become significant on wells which must be treated often. In addition to the cost of lost production time, the high cost of semi-skilled labor adds to the overall cost of using present recirculation treatment methods.